I feel so alone and lost. I feel like God has left me. What do I need to do to fill this emptiness?
There are a number of reasons we can feel alone. Sin can cause a person to feel lonely and so can trouble and disappointment. It is possible as you put it, to fill this emptiness.
First Place To Look
Your key words are “I feel like God has left me.” This is usually due to sin. Sin blocks our relationship with God. This occurs because the Holy Spirit convicts us when we sin (John 16:8-11). In Psalm 51 we discover that after King David had sinned, he was afraid that God would leave him. He was unhappy and miserable.
Make me to hear joy and gladness, let the bones which You have broken rejoice. Hide Your face from my sins and blot out all my iniquities. Create in me a clean heart, O God, and renew a steadfast spirit within me. Do not cast me away from Your presence and do not take Your Holy Spirit from me. Restore to me the joy of Your salvation and sustain me with a willing spirit. (NASB) Psalm 51:8-12
King David’s problem was sin. That would be a good place to start. Start looking for sin in your own life. Ask yourself, “What sin or sins have I committed or am committing?” The sin could be anger or resentment against someone, sexual sins, murder, constant lying, pornography, and stealing for example. Habits that involve repeated sinning will also cause you to feel alone and distant from God. Why? The Holy Spirit is convicting you about your sin. God wants you to stop. You will be miserable until you stop.
Different Kind of Sin
There is also another reason you can feel alone. It involves sin too!
Turn to me and be gracious to me, for I am lonely and afflicted. The troubles of my heart are enlarged; bring me out of my distresses. Look upon my affliction and my trouble, and forgive all my sins. (NASB) Psalm 25:16-19
This sin occurs when troubles come our way and we respond by not trusting God for our situation. Some are not willing to wait on God’s timing for Him to resolve our problems. Again King David responded correctly. He admitted that he had sinned and said that he would wait on God. He would trust God and not worry.
Let integrity and uprightness preserve me, for I wait for You. (NASB) Psalm 25:21
Look for sin. Admit that you have sinned against Him and ask Him to restore your joy. Then ask God to meet your need through your Bible study and Christian fellowships.
But God, who comforts the depressed, comforted us by the coming of Titus . . . (NASB) 2 Cor. 7:6